Glossary

End-of-charge voltage

Unit V · Also Final charge voltage, Absorption voltage

What is End-of-charge voltage?

The voltage up to which a battery is charged. It depends on the battery type and is the value that decides whether a battery bank actually becomes full.

What matters about End-of-charge voltage in practice?

If it is not reached, the battery bank remains permanently partially charged — for lead-acid the road to sulphation, for lithium the reason balancing never takes place and the battery monitor never synchronises.

The most common reason for too low a voltage at the battery is not the regulator but the voltage drop on the charging cable. Charging cables therefore belong in the three-percent category.

Which end-of-charge voltage applies to which battery type?

The values are in the data sheet. As a rough guide for 12 V systems, AGM and flooded batteries are usually around 14.4 to 14.7 V, gel batteries slightly lower and LiFePO4 batteries often between 14.2 and 14.6 V. At 24 V the values double.

Why is it often not reached at the battery?

  • Voltage drop on a charging cable that is too thin or too long.
  • Contact resistance at terminals, fuses and switches.
  • A controller without a sense lead that measures the voltage at the device instead of at the battery.

What else applies to lead batteries?

Lead batteries need a temperature-dependent end-of-charge voltage: slightly higher in the cold, slightly lower in the heat. That is why a temperature sensor belongs on the battery. The page charger and inverter shows which chargers can do this.

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